Chronic lymphocytic leukemia is significantly more common than reported

Chronic lymphocytic leukemia (CLL) is frequently diagnosed by flow cytometric analysis of peripheral blood lymphocytes. Because Tumor Registry data collection usually requires a tissue diagnosis, patients with CLL diagnosed by flow cytometry may fail to be reported to Tumor Registries, which are an important source of epidemiological data. Tumor Registry data may thus significantly underestimate the true incidence of CLL. To test this hypothesis, we reviewed the actual and reported incidence of CLL for 10 years (1990 to 1999) at the Little Rock Veterans Affairs Medical Center (VAMC). Review of medical and laboratory records showed that 93 patients had a new diagnosis of CLL. (Figure Presented) 1990 1991 1992 1993 1994 1995 1996 1997 1998 1999 The Tumor Registry reported 60 new cases of CLL from 1990-1999 (65% of actual total). From 1990-1996, when most diagnoses were based on bone marrow biopsy, the Tumor Registry reported 91 % of newly diagnosed CLL. In 1997, accurate flow cytometry on peripheral blood became readily available at the Little Rock VAMC. Increased use of flow cytometry for diagnosis of CLL was associated with a marked decrease in Tumor Registry reporting. From 1997 to 1999, the Tumor Registry reported a significantly lower 22% of patients with newly diagnosed CLL (P < 0.01, Students t test). Conclusion: Tumor Registry data significantly underestimated the incidence of CLL at the Little Rock VAMC after 1997 due to the failure to include diagnoses made solely by flow cytometric analysis of peripheral blood. Because many hospital Tumor Registries do not routinely monitor flow cytometry results, this may reflect a widespread problem. Our data suggest that the national incidence estimates for CLL based on Tumor Registry data may be low and that the disease may be significantly more common than currently reported. Tumor Registry data collection should be modified to routinely include reports from flow cytometry facilities.